t=0:.01:5;
x=sin(2*pi*t);
figure,plot(t)
y=fft(x(1:101));
figure,stem(abs(y(1:50)))




x2=[x(1:50),x(1:450)];
plot(t(1:500),x2)
y2=fft(x2);
figure,stem(abs(y2(1:50)))
